1. Field of the Invention
The present invention generally relates to a catalytic converter for use with an internal combustion engine to purify exhaust gas emanating therefrom and, more particularly, to a monolithic catalytic converter of the type which uses a honeycomb catalyst carrier.
2. Description of the Prior Art
In a catalytic converter of the type described, a catalyst carrier is housed in a retainer member which is formed of a stainless steel mesh, or in a foamed mat, such as ceramic wool available in the trade name INTERAM MAT from 3M Co. Ltd., U.S.A. The catalyst carrier is put in a generally cylindrical split casing which consists of two casing halves, together with seal members for sealing opposite ends of the casing. The abutting faces of the casing halves are welded or otherwise joined to each other. For details of such a catalytic converter, a reference may be made to Japanese Patent Laid-Open Publication Nos. 212319/1982 and 2412/1983.
Meanwhile, a honeycomb catalyst carrier employed with such a catalytic converter comprises a sintered integral body mainly consisting of SiO.sub.2, Al.sub.2 O.sub.3 and MgO and, therefore, it lacks resistivity against shocks and impacts. In addition to the fragility, the dimensional accuracy of finished honeycomb catalyst carriers is quite rough. For example, where catalyst carriers each having a circular cross-section are produced with a designed diameter of 65 millimeters, the scattering or expected diameter deviation in the actual diameters of the products amounts to a little over 2 millimeters; where catalyst carriers each having an oval cross-section are produced with a designed shorter diameter of 65 millimeters and a longer diameter of 130 millimeters, the scatterings or expected diameter deviations in the two diameters individually amount to a little over 4 millimeters.
Assume a case wherein a catalyst carrier of the type discussed is loaded in the prior art split casing in which the casing halves are clamped together with a predetermined margin at abutting ends thereof. Then, if the catalyst carrier is relatively large-size, the clamping load will be excessive and damage the catalyst carrier while, if the catalyst carrier is relatively small-size, the clamping load will be short and only loosely retain the catalyst carrier to enhance the liability to damage, due to the severe scatterings situation discussed above. The excessive or short clamping load, therefore, is incapable of allowing the prior art catalytic converter to fully exhibit its expected function. While this problem may be solved by increasing or decreasing the number of the retainer members and/or that of the seal members after actually measuring the dimensions of each catalyst carrier such that a predetermined clamping load acts adequately on all the catalyst carriers, such an implementation will increase the number of assembling steps to a degree which is objectionable for quantity production.